The present invention relates to a fume hood apparatus, and more particularly to a fume hood apparatus which produces air flows designed to avoid or otherwise minimize undesirable air turbulence and back flows to improve containment.
A fume hood is a form of ventilated enclosure defining a work space within which a person may extend his arms to conduct experiments, manufactures, or other operations and in which noxious gases, vapors, or the like may arise. To avoid release of the noxious material out into a room in which people may be working, the fume hood is associated with a negative pressure source, such as a fan, for drawing air and noxious material from the enclosure for safe discharge. The fume hood is provided with a front opening which allows access to the enclosure and through which air is drawn to replace that withdrawn by the fan. Examples of known fume hood apparatus are shown by U.S. Pat. Nos. 5,056,422 and 3,041,957.
A problem with known fume hoods, however, is that the flow of air through the access opening is not streamlined and turbulences and eddies are formed, particularly along side walls and in corners of the enclosure, which result in work space air and hence noxious material flowing back through the access opening and out into the room. One effort toward solving this obviously undesirable situation of possible back flow of work space gases, vapors, etc. is to provide cowling over the edges of the access opening such that the air flow over the cowling is streamlined (i.e. smooth) and substantially free of eddies, as disclosed in U.S. Pat. No. 4,409,890. However, the addition of cowling structure to the fume hood access opening unnecessarily complicates the fume hood structure.